The present invention relates to a method and an apparatus for reducing the spread of a hit pattern for a rotationally-stabilized ammunition unit in the form of a projectile, shell or the like, discharged in a ballistic trajectory from a launching device towards a target to be combated. The present invention entails dynamic balancing of the shell in order to reduce differences in air resistance between different shells so as to improve hit probability.
It is previously known in the gunnery art to subject shells to QA inspection and to rectify any thereby ascertained imbalances by the addition of weights or by machining off excess material such that a main axis of inertia coincides with the geometric axis of the shell surface, to eliminate, by such means, deficiencies in the product. Oblique deviations between the geometric axis and the trajectory of the projectile will thereby be avoided, as a result of which variations in air resistance between different shells will be reduced thereby also reducing the spread of shots in a hit pattern.
One drawback inherent in the prior art method is in the difficulty entailed in mechanical rectification of the shell proper as required by the balancing operation without occasioning any further reduction in the overall quality of the finished shell. For example, no modification can be made to the shell casing without resulting in changes to its air resistance. Within the shell, account must be taken of extant devices, for example such that an explosvie charge must, for reasons of safety, be enclosed in an unbroken and smooth-walled cavity. Moreover, adjustment must be affected at two positions on the shell on either side of its point of gravity, seen in the longitudinal direction--or line of trajectory--of the shell.